Preoperatwe pulmonary function: Its correlation to the duration of post-operative mechanical ventilation in spinal fusion patients

Introduction:The use of preoperative pulmonary function testing as a predictor of postoperative complications in children undergoing surgery for kyphoscoliosis is controversial. We sought to determine the association between the degree of impairment of preoperative pulmonary function and the duration of postoperative mechanical ventilation (DMV). Methods:We conducted a retrospective review of 69 patients admitted after spinal fusion surgery. Preoperative forced vital capacity (FVC) and FEV₁ were obtained and classified as: no impairment(NI), nunimal(MI)(71-99%), moderate(MO)(51-70%),or severe impairment(SI)(≤50%) based on the percent of predicted value obtained. Total duration of mechanical ventilation was measured in hours from time of PICU admission until successful extubation. Data were analyzed using ANOVA,and Dunn-Bonferonni association. Percent predicted FVC and FEV₁ were then plotted against time using linear regression analysis. Results: 60/69 had either anterior(A) or anterior and posterior (AP) fusions. 9/69 had posterior fusions(P). Of those having A or AP, 9/60 had a thoracoscopic technique. Three patients required reintubation. The severity breakdown of FVC is as follows: NI 9, MI 37, MO 17, SI 6.The severity breakdown for FEV₁ is as follows: NI 9, MI 35, MO 19, SI 6. There was no statistical difference among severity groups when using FVC impairment(p=.1684)to compare DMV. Statistical significance existed among severity groups based on FEV₁ (p=.0011). Statistical significance also existed with respect to FEV₁ when comparing the most severely impaired to any other group(p=.0024 versus NI, p=.0007 versus MI, p=.0030 versus MO). Linear regression analysis demonstrated no correlation between percent predicted FVC and DMV. A linear relationship did exist between percent predicted FEV₁ and DMV Conclusion:The degree of impairment of preoperative FEV₁ correlated with the duration of postoperative mechanical ventilation in spinal fusion patients. Preoperative FEV₁ can be used as an indicator of anticipated duration of postoperative mechanical ventilatory support.